The present invention relates to an air suspension system for an automotive vehicle, and more particularly to a simplified air suspension system adapted to provide an air spring that functions as a leveling valve to control the inflow and outflow of compressed air in response to transmitted load or vibration.
Generally, suspension systems have been developed with a view to alleviating shock transmitted from rough terrain to the vehicle body to thereby improve the safety and comfort of riding in a vehicle. One such suspension system is an air suspension system. In this system, the supply and discharge of compressed air is controlled to control the height of the vehicle in response to weight and to suppress changes in the position of the vehicle to provide stability while the vehicle is in motion.
However, prior art air suspension systems generally have a relatively large number of component parts, such as the leveling valve, a lever connected to the rocker of the leveling valve, and a rod connected to the lever and to an axle supporter mounted with the axle. Also, such air suspension systems must take into account interference between related parts of the lever, rod and correlated parts, resulting in difficulty in layout of component parts and design thereof.
The present invention provides an air suspension system for an automotive vehicle adapted to provide a leveling function within an air spring to control the inflow and outflow of compressed air in response to a load or vibration transmitted from rough terrain or from carrying weight of the vehicle while the vehicle is in motion. In accordance with one embodiment of the present invention, a valve body is mounted in an inner upper portion of a bellows. The valve body has communicating passages for supplying pressurized air into the bellows or for discharging the pressurized air out of the bellows. A piston is installed underneath the bellows. A valve operating means is provided to switch the open/closed state of the communicating passages in response to relative movement of the piston and the valve body.
In a further alternative embodiment of the present invention, an air suspension system for a vehicle preferably includes at least one air spring. In a preferred embodiment, the air spring comprises a bellows, a piston and a valve. The bellows defines a closed space and is adapted to be secured to a portion of the vehicle at an upper end thereof. The piston is disposed at a lower end of the bellows and the bellows is secured around the piston with an air-tight seal. The valve is disposed within the bellows and communicates with a source of pressurized air. The valve also cooperates with the piston to control flow of pressurized air into and out of the bellows in response to up and down motion of the piston as the vehicle moves over the terrain.
Preferably, the valve includes a valve body mounted in an upper portion of the closed space defined by the bellows. The valve body is adapted to be fixed to move with the frame of the vehicle and defines plural air passages. A first air passage provides pressurized air. A second air passage exhausts to atmosphere and leads into the closed space. The first air passage joins the second air passage at a first branch point. A third air passage joins the second air passage at a second branch point, above the first branch point, and communicates with the closed space. A linkage is received at one end in the second air passage and is operatively linked to the piston at an opposite end. A first seal is mounted on the linkage and slideably received in the second air passage to control communication between the second air passage and the closed space, thereby selectively permitting pressurized air to flow into the closed space. A second seal is mounted on the linkage above the first seal. The second seal provides selective communication between the second and third air passages in response to movement of the piston.
In further preferred embodiments, the suspension system of the present invention includes an axle support member on which a vehicle axle and wheel are mounted, with piston being secured to the axle support member. At least two air springs may be mounted on the axle support member. Also, the system may include a pressurized air tank mounted on the vehicle to provide the source of pressurized air.